A. Field of the Invention
This invention is related with the treatment of polluted metal mechanic industrial wastewater and urban water and more specifically with a method for the treatment of waste water from industrial processes as well as the so called xe2x80x9cblackxe2x80x9d water of the urban nets by adding ferrous chloride or acid liquors of the same, specifically with a spent pickling liquor containing ferrous chloride and hydrochloric acid, as resulting from industrial processes at the metal-mechanic industry.
B. Description of the Related Art
Mexican metallurgic industry, after privatization, has had a substantial increasing in production of steel and consequently of export products derived from the steel, such as the laminated steel, reaching 1.4 million tons of exports in 1996, and increasing the internal consumption of this product by a 34.5%.
However the industrial production of laminated steel, generates a great amount of industrial waste, among which is the spent pickling liquor containing ferrous salts and hydrochloric acid, which have been considered as a dangerous waste and consequently it has to be processed by the companies generating them or, as a last resource, said companies have to provide confinements for these dangerous residuals, controlled by the regulations, at a high cost that in turn strike directly in the production costs of the laminated steel. Some companies decompose this liquor by combustion, in order to recover hydrochloric acid and iron oxides. The hydrochloric acid is recycled to the pickling process and the iron oxides are marketed as pigments or for other uses.
The process for the decomposition of the pickling liquor is usually carried out by combustion in a furnace constructed with a refractory lining having a high content of silica, having a useful life of 5 to 7 years, so that the intensive consumption of energy required for the decomposition, joined to the considerable investment of the required equipment and the low price of the resulting acid and oxides, makes this process very expensive, and consequently the only justification of the same is just for ecological reasons.
However, such processes are not of the zero emission type since there are losses in the order of 2.3 to 31.75 kg. of hydrochloric acid per ton of processed pickling liquor.
As a consequence of these issues, Applicants conducted a deeply research about the properties of the pickling liquor, as starting point for their analysis, founding that the pickling liquor did not have the presence of heavy toxic metals such as: mercury, cadmium, selenium, chromium, lead, etc. and that its typical composition was: 220 g/l of ferrous salts; 15 g/l of hydrochloric acid, in approximately 940 ml. of water whose combination confers it very specific properties for the use in the treatment of industrial and urban water.
Applicants have found that contacting the waste water from the industrial processes as well as the polluted black water of the urban nets, with ferrous chloride or its acidic liquors, a clarifying flocculus of organic material is formed, derived from the precipitation of the ferrous ion, which adsorbs the organic matter (proteins, fatty, oil, carbohydrates, detergents) of this polluted water, by which it is possible to obtain water with a very low content of pollutants. Therefore, observing that the spent pickling liquor resulting from the processes of the metal-mechanic industry, mainly contains ferrous salts and hydrochloric acid, Applicants found that this spent pickling liquor can be used as the acidic liquor of the ferrous chloride in the direct physical-chemical treatment of the polluted water.
A method of removing soluble sulfide residue and organic compounds from industrial waste water is disclosed in the U.S. Pat. No. 4,419,247 of Tenny, which comprises the steps of adding to said scrubber water waste an acidic copper waste in an amount whereby the copper ion added is sufficient to precipitate no more than 90 percent of the sulfide ion present, removing the precipitated copper sulfide, and thereafter adding a pickle acid waste containing ferrous ions in an amount sufficient to essentially completely react with all sulfide present and to precipitate as an iron-copper sulfide mixture.
The objective of Tenny""s method, is to treat only small amounts of scrubbed water waste produced by the process for the manufacturing polyolefins from natural gas, containing sulfide and cyanide, in order to produce a caustic water to be treated for recovering sodium hydroxide. Therefore Tennys""s process necessarily comprise firstly adding an acidic copper waste and then adding a pickle acid waste containing ferrous ions to precipitate iron sulfide and ferrocyanide, as well as small amounts of oil.
In fact, the main reactive used in Tenny""s method is the acidic copper waste and use a small amount of pickle acid waste just to complete the reaction with the sulfide and precipitate as an iron-copper sulfide. The, main objective of Tenny""s method is to eliminate sulfide and cyanide by the precipitation of iron sulfide and ferrocyanide in order to produce a caustic water to be treated for recovering sodium hydroxide, whereas applicant""s process main objective is to treat great amounts of metal-mechanic industrial waste water and urban water containing great amounts of oil, protein and organic material, in order to obtain great volumes of clean water which can be recycled even for human consumption which is not disclosed or even suggested by Tenny.
Furthermore, Tenny does not disclose nor remotely suggest the formation of a flocculus of organic material whereas applicant""s process promotes the use of ferrous chloride for the formation of a flocculus of said organic material, by taking advantage of the so named xe2x80x9cZ factorxe2x80x9d in order to denaturalize the proteins contained in the waste water and promote the formation of said flocculus, which was not recognized nor remotely suggested by Tenny.
With applicants method, it is possible to obtain water with a very low content of pollutantsxe2x80x94even for human consumexe2x80x94allowing at the same time a re-use of the spent pickling liquor whose final destination, at the present time, is the confinement and/or the decomposition, with polluting consequences for the environment.
It is therefore a main objective of the present invention, to provide a process for the treatment of polluted metal-mechanic industrial waste water and urban water, by adding ferrous chloride or their acidic liquors, in order to form a clarifying flocculus of organic material derived from the precipitation of the ferrous ion that adsorbs the organic matter such as the proteins, fatty, oil, carbohydrates and detergents, contained in this polluted water.
It is also a main objective of the present invention, to provide a process for the treatment of polluted metal-mechanic industrial waste water and urban water, of the above disclosed nature, by using the spent pickling liquor resulting from the processes of the metal-mechanic industry mainly containing ferrous salts, hydrochloric acid and water mainly, as the acidic liquor of the ferrous chloride.
It is an additional objective of the present invention, to provide a process for the treatment of polluted metal-mechanic industrial waste water and urban water, of the above disclosed nature, which avoids the necessity of confining and/or decomposition of the spent pickling liquor resulting from the metal-mechanic industry having polluting consequences for the environment.
It is still an additional objective of the present invention, to provide a process for the treatment of polluted metal-mechanic industrial waste water and urban water, of the above disclosed nature, which avoids the enormous costs derived of the process of decomposition and/or confinement of such spent pickling liquor.
These and other objectives and advantages of the present invention, will be apparent to the persons having ordinary skills in the art, from the teachings of the following description of the specific embodiments of the invention, represented by the following examples for carrying out this process.